Process for the manufacture of acrylic synthetic fiber



United States Patent 3,121,765 PROCESS FOR THE MANUFACTURE OF ACRYLICSYNTHETIC FIBER Ichiro Kanda, Miciliaiti Nakaiima, and Makoto Amiya,

all of Kitaiima-machi, Itano-gun, Tokushima Prefecture, .Iapan,assignors to Tolio Rayon Kahushiki Kaisha, Tokyo, Japan, a corporationof Japan No Drawing. Filed Sept. 18, 1961,. Ser. No. 138,581 Claimspriority, application Japan Sept. 24, 1960 4- Claims. (Cl. 264-182) Thisinvention relates to a process for the manufacture of a syntheticacrylic fiber by spinning a spinning solution comprising zinc chloridesolution and polymer containing acrylonitrile as a principalconstituent, and then treating .the coagulated tow with an aqueoussolution of a compound so as to produce a zinc complex ion with theobject of avoiding the degradation of fiber quali ty due to remainingsalts.

It has been reported that in fiber products obtained from an acrylicpolymer solution using concentrated aqueous inorganic salt solutioncontaining zinc chloride as a principal constituent, inorganic saltsparticularly zinc compound in the form of hydroxide or oxide remained inthe fibers and that such residual salts caused the quality of theproducts to be unfavorably reduced. For instance, fiber containing aresidual salt of more than 1 percent by weight is brittle and dyed indull color, and upon heating it becomes yellowish and weak. To improveon the above disadvantages, it has been proposed to apply anion-exchange resin method of Japanese Pat. Publn. No. 2,369/ 56, or azinc chloride method by treating the fiber with compounds such as sodiumethylenediamine tetraacetate according to the Japanese Pat. Publn. No.8,444/57. But these methods are too expensive for industrial practice.

The present invention has been reached by our new knowledge on theeffect of compounds, forming complex ion with zinc ion, such asammonium, amine or chlorine, and the process is industrially useful andpracticable.

Desalting agents, in the present invention, are sodium chloride,potassium chloride, ammonium chloride, urea, thiourea and others, thatis, election donor compounds which coordinate to cation forming complexion. These compounds which have chloride, ammonium ion, or amino groupcan form complex ions with the zinc ion as in the following. Halides,such as NaCl, KCl, NH Cl form complex ions, some of which are [ZnCld and[ZnCl 0H and in the case of NH Cl occur, moreover, amine complexes, suchas and so on. In the case of urea and thiourea occur [ZH(NHQCONHQ)4]++and [ZI1(NH2CSNH2)4]++ respectively. All of these complex ions havetetrahedral 4-coordinated structure.

The salt removal treatment based on the above discovery may be appliedto a dried fiber, but from the point of easiness in removing the saltand of simplification in industrial fiber process, it is effected duringor after the washing process of coagulated tow with water which has beencoagulated from a spinning solution as is a common practice, and thenthe coagulated tow is treated with an aqueous solution of abovementioned compounds.

According to this invention, by immersing tow after being passed throughthe coagulating bath in an aqueous solution of desalting agents, zinccompounds, which remained in the tow as hydroxide or hydrated oxide ofzinc, can diffuse and dissolve out into the solution as water solublecomplex ions.

The tow which is formed by extruding a polymer solu- 3,121,765 PatentedFeb. 18, 1964 tion into a coagulating bath comprised of a more diluteaqueous salt solution of the same or similar salt system as employed inthe solvent of the polymer solution, may be stretched at moderatetemperature in water, or stretched under moderate temperature andhumidity after water washing. Thereafter, it may go through requiredaftertreatments, such as oiling, heat stretching and relaxing processesthat are in common practice.

The salt removing treatment is accomplished, according to thisinvention, by using 1 to 20 percent aqueous solution of desalting agent,preferably 5 to 15 percent, at 70 C. to boiling temperature, preferablyover C.

Results according to a few examples of salt removal treatment are shownin the following Table 1, using coagulated tow B in the followingExample 1. Tow B is composed of 52.6% polymer, 45.1% water and 2.3% zincchloride, and, when squeezed and dried in air, it contains 0.39%residual zinc.

T he tow B treated with various salt removal treatments (I, II, III, IVand V) and dried in air to 1 percent moisture content was analyzed andfound to include residual zinc chloride as follows:

TABLE 1 Method I II III IV V Residual ZnCl Percent 0.173 0.150 0.0240.026 0.029

invention, but are not to be construedas limiting.

Example 1 A solution was prepared consisting of 9% by weight ofcopolymer containing mole percent of acrylonitrile and 5 mole percent ofmethyl acrylate having a Standinger molecular weight of 82,000, 50.9% byweight of zinc chloride and 41% of water. This solution, having aviscosity of 360 poises at 30 C., was extruded through a -hole spinnerethaving openings respectively 0.08 mm. in diameter, into an aqueoussolution of 15% by weight of zinc chloride at 15 C. The so-coagulatedtow of filament was stretched 1.6 times its original length duringwashing with water (the sample here called A), and then stretched inboiling water three times its cold stretched length (sample B). This towB of stretched fibers was washed with water and, when dried in air to 1%moisture content, had 0.39% of zinc chloride. This tow was boiled in anaqueous solution of 5% by weight of ammonium chloride for 2 minutes,then washed with water and, when dried, had 0.024% of zinc chloride.

Example 2 The tow A in Example 1 was stretched in boiling watercontaining 7% of sodium chloride two times its original length and thenin boiling water 5 times its original length, and when dried, had only0.034% of zinc chloride in it.

Example 3 The other portion of tow A was treated with aqueous solutionof 10% of urea, washed with water and, when dried, had 0.039% of zincchloride. The other portion of tow B was treated similarly as A and hadhad only 0.029% of zinc chloride.

What we claim is:

1. A method for manufacturing acrylic synthetic fibers comprisingspinning into a coagulated tow a solution of a polymer containingacrylonitrile and a solvent of aqueous zinc chloride, contacting thecoagulated toW with an aqueous solution containing 1 to 20 percent of adesalting agent chosen from the group consisting of ammonium chloride,sodium chloride, potassium chloride, urea and thiourea, and maintainingthe aqueous solution in a temperature range of from 70 to 100 C.

2. The method as recited in claim 1, wherein the aqueous solutioncontains 5 to percent of the desalting agent.

3. A method for manufacturing acrylic synthetic fibers comprisingspinning into a coagulated tow a solution of a polymer containingacrylonitrile and a solvent of aqueous zinc chloride, contacting thecoagulated tow With an aqueous solution containing 1 to percent of adesalting agent chosen from the group consisting of ammonium chloride,sodium chloride, potassium chloride, urea and thiourea, and maintainingthe aqueous solution in a temperature range of from to C.

4. The method as recited in claim 3, wherein the aqueous solutioncontains 5 to 15 percent of the desalting agent.

References Cited in the file of this patent

1. A METHOD FOR MANUFACTURING ACRYLIC SYNTHETIC FIBERS COMPRISINGSPINNING INTO A COAGULATED TOW A SOLUTION OF A POLYMER CONTAININGACRYLONITRILE AND A SOLVENT OF AQUEOUS ZINC CHLORIDE, CONTACTING THECOAGULATED TOW WITH AN AQUEOUS SOLUTION CONTAINING 1 TO 20 PERCENT OF ADISALTING AGENT CHOSEN FROM THE GROUP CONSISTING OF AMMONIUM CHLORIDE,SODIUM CHLORIDE, POTASSIUM CHLORIDE, UREA AND THIOUREA, AND MAINTAININGTHE AQUEOUS SOLUTION IN A TEMPERATURE RANGE OF FROM 70* TO 100*C.